A Voltage Equalization Control Method for Optimizing MMC Average Switching Frequency

Abstract

The invention discloses a voltage equalization control method for optimizing the average switching frequency of MMC. Taking the sub-module rotation number optimization method as the core, the marking input group and the input group are reordered to form a reordering group, and the reordering group is selected from the reordering group. The sub-modules are set to cut off, and the sub-modules that are not selected as cut-off in the marked input group are set to be turned on, which effectively avoids the situation that the voltage of individual sub-modules in the input group is higher or lower than the voltage of individual sub-modules in the cut-off group, and eliminates the Non-essential sub-modules are switched in rotation, which can not only ensure the voltage balance effect, but also reduce the switching frequency of the MMC system. On the basis of the sub-module rotation number optimization method, the present invention determines whether to start the sub-module rotation number optimization program under actual operating conditions by adding a pre-judgment, so that the switching frequency can be further reduced.

Description

technical field [0001] The invention belongs to the technical field of power system transmission and distribution, and in particular relates to a voltage equalization control method for optimizing the average switching frequency of an MMC. Background technique [0002] Modular multilevel converter (MMC) is different from two-level and three-level converters. It adopts a cascade of multiple sub-modules, which has high scalability, high output waveform quality, and low loss. It has gradually become a research hotspot in the field of HVDC transmission. With the continuous improvement of capacity and voltage level, the number of neutron modules and power semiconductor devices in high-voltage and large-capacity MMC systems also increases rapidly, which leads to the increasingly prominent problem of converter valve operating loss. [0003] At present, the MMC-HVDC systems that have been put into operation at home and abroad have widely adopted the nearest level modulation (NLM) a...

AI Technical Summary

Problems solved by technology

[0005] Aiming at the deficiencies of the above-mentioned technologies, the present invention provides a voltage equalization control method that optimizes the average switching frequency of the MMC, which solves the problem that the existing technology cannot dynamically adjust the fixed rotation number according to the switching status of the sub-modules in the bridge arm under different circumstances, resulting in unreasonable Technical issues of necessary sub-module rotation switching

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